Gardening with Gary

Gardening Advice from an Expert

Grapes

Cat Lady writes~ My grapes have started to grow, but there are so many vines that keep growing. Do I need to prune those back so that the grapes will get the sun or do I leave them? And if I prune them back how far back to I prune?

A. The biggest problem with home grape growers is that they don't prune their vines enough. When pruning, you should remove the majority of wood produced the previous season - about 90 percent is pruned off. The time to prune grapevines is now, from January through March 1, when the grapes are dormant.

There are two types of grape pruning - cane pruning and spur pruning. Mature plants should be pruned yearly to remove all growth except new one-year-old fruiting canes and renewal spurs.

Grapes are produced from buds that will grow into shoots on one-year old canes. The most fruitful canes will be those that were exposed to light during the growing season, are thicker than a pencil in width and as close to the trunk as possible (when cane pruned).

To cane prune, select two to four new fruiting canes per vine. Cut back each of these to leave about 15 buds per cane. For wine grapes, leave about 20 to 30 buds per plant. In table grapes, leave 50 to 80 buds per plant. Leave a one-or two-bud spur cane near the fruiting cane with one or two buds each. These "renewal spurs" will produce the fruiting canes for the following year and thus maintain fruiting close to the trunk. All other cane growth should be pruned off.

To spur prune, prune along main canes to leave two-to three-bud spurs, each four to six inches apart. Leave no more than 20 to 80 buds per plant, depending on the type of grape. Remove all other one-year-old wood.

The Oregon State University Extension Service offers an illustrated 14-page publication on growing, pruning and trellising grapes "Growing Grapes in Your Home Garden," EC 1305. http://eesc.orst.edu/agcomwebfile/edmat

Pruning is probably the most important part of grape culture. Because of the grape's tendency to grow so vigorously a lot of wood must be cut away each year. Grape vines that are overgrown become so dense that the sun cannot reach into the area where fruit should form.

The second year, very early in the spring, before the buds swell, cut the vine back to a single stem with no branches. This will strengthen the trunk and encourage more vigor. During the year, allow four side branches to grow (two in each direction) and train them along wires. Pinch off all other buds that are inclined to grow in other directions.

By the end of the second year, these vines should bloom but produce a few grapes the third year. During the third year, four more canes should be allowed to grow from buds along the main stem. These should parallel the vines producing grapes and will replace the first four canes. In late winter following the third year, cut out the old canes that produced the past year and tie the new ones to the wires to replace them. Trim off all excess growth except the four new canes.

Treated in this way, each mature vine should produce from 12 to 15 pounds of grapes or 30 to 60 bunches per year. If more bunches than this are produced, remove them before the grapes develop, to avoid overbearing and thus weakening the plant. Vines should continue to produce well for many years.

Assistance from The Kemper Center for Home Gardening